Syntheses, Structures, and Properties of Tricyclo[5.1.1.13,5

Thiostannate Tin-Tin Bond Formation in Solution: In Situ Generation of the Mixed-Valent, Functionalized Complex [{(RSn IV ) 2 (μ-S) 2 } 3 Sn III 2 S ...
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Organometallics 1997, 16, 4428-4434

Syntheses, Structures, and Properties of Tricyclo[5.1.1.13,5]tetrasilachalcogenanes (Thex2Si2E2)E2 (E ) S, Se) and Tricyclo[5.1.1.13,5]tetragermachalcogenanes (Thex2Ge2E2)E2 (E ) S, Se) Masafumi Unno, Yuuki Kawai, Hiroaki Shioyama, and Hideyuki Matsumoto* Department of Applied Chemistry, Faculty of Engineering, Gunma University, Kiryu, Gunma 376, Japan Received May 27, 1997X

Reactions of ThexSiCl3 (Thex ) 1,1,2-trimethylpropyl) with Li2S and Li2Se in tetrahydrofuran at room temperature afforded the tricyclo[5.1.1.13,5]tetrasilachalcogenanes (Thex2Si2S2)S2 (1) and (Thex2Si2Se2)Se2 (2), respectively. Similar reactions of ThexGeCl3 with Li2S and Li2Se gave the tricyclo[5.1.1.13,5]tetragermachalcogenanes (Thex2Ge2S2)S2 (3) and (Thex2Ge2Se2)Se2 (4), respectively. X-ray crystallography of 1-4 reveals that these molecules were isomorphous and possess strained “double-decker”-like frameworks (Candiani structure). Compounds 1 and 3 show isomerization at 190 °C to the adamantane-like systems, tricyclo[3.3.1.13,7]tetrasilathiane (5) and tricyclo[3.3.1.13,7]tetragermathiane (6), respectively. For 4, isomerization to the adamantane cage takes place at much lower temperature (e.g., 80 °C), indicating that Ge-Se double-decker-like cage is more reactive than Si-S and Ge-S cages. Introduction Silicon and germanium sesquichalcogenides are of interest because of their intriguing structure and properties.1 For tetrasilachalcogenanes (RSiE1.5)4 and tetragermachalcogenanes (RGeE1.5)4, two structures are possible: adamantane-like cages and “double-decker”like cages. From the consideration of ring strain, the adamantane cage has been expected to be more likely than the double-decker-like one, and most of the previous work dealt with the synthesis of silicon-sulfur,2 silicon-selenium,3 germanium-sulfur,4 and germaniumselenium5 adamantane cage structures. The synthesis of compounds with the double-decker structure had not been reported until 1992,6 when Ando and co-workers prepared the tricyclo[5.1.1.13,5]tetragermathiane (t-Bu2Ge2S2)2S2 in 30% yield by the reaction of t-BuGeCl3 with (NH4)2S5 in THF.7 A similar structure was also observed in 1995 by Merzweiler in the transition metalAbstract published in Advance ACS Abstracts, September 15, 1997. (1) Armitage, D. A. In The chemistry of organic silicon compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons Ltd.: London, 1989; pp 1401-1409. (2) (a) Forstner, J. A.; Muetterties, E. L. Inorg. Chem. 1966, 6, 552. (b) Feher, F.; Luepschen, R. Z. Naturforsch. 1971, 26B, 1191. (c) Kobelt, v. D.; Paulus, E. F.; Schere, H. Acta Crystallogr. 1972, B28, 2323. (d) Bart, J. C. J.; Daly, J. J. J. Chem. Soc. Dalton Trans. 1975, 2063. (e) Haas, A.; Hitze, R.; Kru¨ger, C.; Angermund, K. Z. Naturforsch. 1984, 39B, 890. (f) Bahr, S. R.; Boudjouk, P. Inorg. Chem. 1992, 31, 712. (3) References 2a, e, and f. (4) (a) Moedritzer, K. Inorg. Chem. 1967, 6, 1248. (b) Benno, R.; Fritchie, C. J. J. Chem. Soc., Dalton Trans. 1973, 543. (c) Bochkarev, M. N.; Maiorova, L. P.; Vyazankin, N. S.; Razuvaev, G. A. J. Organomet. Chem. 1974, 82, 65. (d) Pohl, S. Angew. Chem., Int. Ed. Engl. 1976, 15, 162. (e) Pohl, S.; Seyer, U.; Krebs, B. Z. Naturforsch. 1981, 36B, 1432. (f) Haas, A.; Kutsch, H.-J.; Kru¨ger, C. Chem. Ber. 1987, 120, 1045. (5) In addtion to ref 4f: Krebs, B. Angew. Chem., Int. Ed. Engl. 1983, 22, 113. (6) The compound with double-decker structure was first observed in P4(i-PrN)6: Schere, O. J.; Anders, K.; Kru¨ger, C.; Tsay, Y.-H.; Wolmersha¨user, G. Angew. Chem., Int. Ed. Engl., 1980, 25, 81.

substituted compounds, [(Cp′(CO)2FeSi]4E6 (Cp′ ) methylcyclopentadienyl, E ) S, Se).8 As a part of our study of the chemistry of polyhedral compounds containing silicon and germanium,9 we attempted to prepare tetrasilsesquichalcogenides and tetragermsesquichalcogenides with double-decker structures. In a previous communication, we reported the synthesis of tetrathexyl-2,4,6,8,9,10-hexathia-1,3,5,7-tetrasilatricyclo[5.1.1.13,5]decane (1),10 which is the first example of the double-decker-like cage composed of silicon and sulfur (thexyl or Thex denotes 1,1,2-trimethylpropyl hereafter). In this paper, we present the syntheses, structures, and properties of silicon-chalcogenide and germaniumcharcogenide double-decker cages, (Thex2Si2S2)S2 (1), tetrathexyl-2,4,6,8,9,10-hexaselena-1,3,5,7-tetrasilatricyclo[5.1.1.13,5]decane ((Thex2Si2Se2)Se2, 2), tetrathexyl-2,4,6,8,9,10-hexasila-1,3,5,7-tetragermatricyclo[5.1.1.13,5]decane ((Thex2Ge2S2)S2, 3), and tetrathexyl2,4,6,8,9,10-hexaselena-1,3,5,7-tetragermatricyclo[5.1.1.13,5]decane ((Thex2Ge2Se2)Se2, 4). (see Chart 1.)

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Results and Discussion Synthesis. Ando and co-workers reported that, in the reactions of t-BuGeCl3 with (NH4)2S5 and H2S/ C5H5N, reactions proceeded via completely different (7) (a) Ando, W.; Kadowaki, T.; Kabe, Y.; Ishii, M. Angew. Chem., Int. Ed. Engl. 1992, 31, 59. (b) Ando, W.; Kadowaki, T.; Watanabe, A.; Choi, M.; Kabe, Y.; Erata, T.; Ishii, M. Nippon Kagaku Kaishi 1994, 214. (8) Merzweiler, K. In Organosilicon Chemistry II; VCH: Weinheim, Germany, 1995; pp 536. (9) (a) Unno, M.; Higuchi, K.; Ida, M.; Shioyama, H.; Kyushin, S.; Matsumoto, H.; Goto, M. Organometallics 1994, 13, 4633. (b) Unno, M.; Shioyama, H.; Ida, M.; Matsumoto, H. Organometallics 1995, 14, 4004. (c) Unno, M.; Yokota, T.; Matsumoto, H. J. Organomet. Chem. 1996, 521, 409. (d) Unno, M.; Shamsul, B. A.; Saito, H.; Matsumoto, H. Organometallics 1996, 15, 2413. (10) Unno, M.; Shioyama, H.; Matsumoto, H. Phosphorus, Sulfur Silicon Relat. Elem., in press.

© 1997 American Chemical Society

Tricyclotetrasilachalcogenanes and -tetragermachalcogenanes

Organometallics, Vol. 16, No. 20, 1997 4429

Scheme 1

Chart 1

intermediates, depending on the sulfurization reagent. They indicated that a mild sulfurization reagent like (NH4)2S5 might make a kinetically controlled reaction possible, affording the double-decker cage compound (tBu2Ge2S2)2S2. In our work, we employed Li2S or Li2Se (generated in situ in tetrahydrofuran, THF)11 for the reaction with RSiCl3 and RGeCl3 and found that the selection of the substituents is also important in the formation of the double-decker structure. For example, the sulfurization of t-BuSiCl3 with Na2S in THF afforded the adamantane cage compound tetra-tert-butyl-2,4,6,8,9hexathia-1,3,5,7-tetrasilatricyclo[3.3.1.13,7]decane in 11% yield.10 However, on treatment of ThexSiCl3 with 1.5 equiv of Li2S in THF, (Thex2Si2S2)2S2 (1) was formed in 25% yield. We feel that the less symmetrical structure of the thexyl group as well as its steric congestion may favor the formation of the Si2S2 four-membered ring. By the reaction of ThexSiCl3 and ThexGeCl3 with Li2S and Li2Se, (Thex2Si2Se2)2Se2 (2), (Thex2Ge2S2)2S2 (3), and (Thex2Ge2Se2)2Se2 (4) were obtained in good yields. The results are summarized in Scheme 1. Isolation of these compounds was easily affected (see Experimental Section). X-ray Structures. The structures of 1-4 were unequivocally established by X-ray crystallography. Crystallographic data, selected bond lengths and angles and nonbonding atom distances are given in Tables 1-5. The ORTEP drawings are shown in Figure 1. All the compounds crystallize in the C2/c space group and have a twofold symmetry axis in the center of the eightmembered ring, and the lattice parameters are very close each other. The Si4S6 core of 1 consists of two planar Si2S2 rings which are linked by two bridging sulfur atoms. The Si-S bond lengths in 1 showed no difference between four- and eight-membered rings (11) Gladysz, J. A.; Hornby, J. L.; Garbe, J. E. J. Org. Chem. 1978, 43, 1204.

(2.132(2) vs 2.136(2) Å). The average bond length of 2.133(2) Å is slightly longer than that of adamantanetype Me4Si4S6 (2.129 Å).2c An interesting feature of this compound is the very close intramolecular atom distance. In the four-membered rings, the distance of the opposite silicon atoms (Si(1)‚‚‚Si(2)) was 2.82 Å. This value is much lower than the sum of van der Waals radii (4.10 Å). Also for sulfur, the S(2)‚‚‚S(3) distance was 3.19 Å and much less than the sum of van der Waals radii (3.60 Å). Obviously this phenomenon resulted from the formation of four-membered rings where bond lengths could not compensate for the atom repulsion. In addition, electronic repulsion of two sulfur atoms might be the reason for shorter Si-Si distance. Very close atom distances were also observed in (Mes2SiO)2 (2.31 Å for Si atoms)12 and the Si-O-C-O skeleton of [(Me5C5)2SiO2]2C (2.18 Å for Si and C atoms),13 both in four-membered rings. For 2, the average Si-Se bond length was 2.278(2) Å, slightly shorter than that of [Cp′(CO)2Fe]4Si4Se6 (2.291(3)-2.306(3) Å).8 The nonbonding distances for Si atoms are more than that of 1, while the distance between Se atoms is slightly shorter than the sum of van der Waals radii (3.53 vs 3.80 Å). Compared with the double-decker tetragermathiane t-Bu4Ge4S6 (average 2.234 Å for Ge-S),7 3 possesses slightly shorter Ge-S lengths (average 2.227(2) Å). This length is longer than those of adamantane-type tetragermathiane: 2.218(2) Å for Me4Ge4S6,4b and 2.210(2) Å for (CF3)4Ge4S6.4f For 4, the Ge-Se bond lengths were 2.358(2)-2.364(2) Å (average 2.361(2) Å), for (CF3Ge)4Se6,4f the Ge-Se bond length was reported to be 2.344(1) Å, and 4 showed a little longer value presumably reflecting the bulkier thexyl groups. Properties. The obtained tricyclo[5.1.1.13,5]tetrasilachalcogenanes and tricyclo[5.1.1.13,5]tetragermachalcogenanes form colorless (1-3) and pale yellow (4) crystals which are soluble in common organic solvents (benzene, toluene, cyclohexane, THF, chloroform). They are surprisingly stable toward hydrolysis, and the exceptional inertness of the Si-S, Si-Se, Ge-S, and Ge-Se bonds in 1-4 can be seen in their stability even in concentrated hydrochloric acid. For example, 3 remained undecomposed upon exposure to concentrated hydrochloric acid for 1 week at room temperature, indicating the thexyl group is an efficient protective moiety for conferring kinetic stability upon the doubledecker framework. (12) Fink, M. J.; Haller, K. J.; West, R.; Michl, J. J. J. Am. Chem. Soc. 1984, 519, 124. (13) Jutzi, P.; Eikenberg, D.; Mo¨hrke, A.; Neumann, B.; Stammler, H.-G. Organometallics 1996, 15, 753.

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Table 1. Summary of Crystal Data, Data Collection, and Refinement 1

2

3

4

formula mol wt cryst description cryst size, mm cryst syst space group a, Å b, Å c, Å b, deg V, Å3 Z

C24H52Si4S6 645.38 colorless prisms 0.2 × 0.2 × 0.2 monoclinic C2/c 15.669(3) 17.007(2) 13.302(2) 97.28(1) 3516.1(8) 4

Crystal Data C24H52Si4Se6 926.78 colorless prisms 0.4 × 0.4 × 0.3 monoclinic C2/c 15.862(3) 17.360(3) 13.227(2) 99.54(1) 3592.0(9) 4

C24H52Ge4S6 823.39 colorless prisms 0.4 × 0.4 × 0.3 monoclinic C2/c 15.875(3) 17.293(3) 13.161(2) 99.33(1) 3565.4(7) 4

C24H52Ge4Se6 1104.79 pale yellow prisms 0.3 × 0.3 × 0.1 monoclinic C2/c 16.139(2) 17.471(2) 13.234(1) 100.665(7) 3667.3(5) 4

diffractometer radiation (λ, Å) µ, mm-1 variation of stds, % 2θ range, deg scan type scan width, deg no. of reflns measd no. of indepd reflns 2709 no. of obsd reflns (|Fo| g 3σ(Fo))

Rigaku AFC7S Cu KR (1.5418) 4.991 0 4-120 ω-2θ 1.05 + 0.30 tan θ 2824 2779 1770

Data Collection Rigaku AFC7S Cu KR (1.5418) 8.575 0 4-120 ω-2θ 1.10 + 0.30 tan θ 2893 2755 2425

Rigaku AFC7S Cu KR (1.5418) 7.262 0 4-120 ω-2θ 1.26 + 0.30 tan θ 2869 2839 2428

Rigaku AFC7S Cu KR (1.5418) 10.674 0 4-120 ω-2θ 1.52 + 0.30 tan θ 2953

structure soln R Rw weighting scheme S (∆/σ)max (∆F)max, e Å-3 (∆F)min, e Å-3 no. of params

SHELXS86 0.052 0.047 w ) 1/σ2(Fo) 2.35 0.08 0.39 -0.33 227

SHELXS86 0.039 0.046 w ) 1/σ2(Fo) 3.24 0.01 0.93 -0.51 155

SHELXS86 0.042 0.038 w ) 1/σ2(Fo) 2.58 0.01 0.97 -0.59 155

Solution and Refinement SHELXS86 0.040 0.044 w ) 1/σ2(Fo) 3.30 0.01 0.90 -0.81 155

Table 2. Selected Bond Lengths (Å), Nonbonding Distances (Å), and Bond Angles (deg) for 1 Bond Lengths 2.139(2) S(1)-Si(2) 2.128(2) S(2*)-Si(2) 2.135(2) S(3*)-Si(2) 1.893(6) Si(2)-C(7)

S(1)-Si(1) S(2)-Si(1) S(3)-Si(1) Si(1)-C(1) Si(1)-Si(2*) S(1)-S(1*)

Nonbonding Atom Distances 2.82 S(2)-S(3) 5.25

Si(1)-S(1)-Si(2) Si(1)-S(3)-Si(2*) S(1)-Si(1)-S(3) S(2)-Si(1)-S(3) S(3)-Si(1)-C(1) S(1)-Si(2)-S(3*) S(2*)-Si(2)-S(3*) S(3*)-Si(2)-C(7)

Bond Angles 110.68(9) Si(1)-S(1)-Si(2) 83.08(9) S(1)-Si(1)-S(2) 114.2(1) S(1)-Si(1)-C(1) 96.82(9) S(2)-Si(1)-C(1) 111.2(3) S(1)-Si(2)-S(2*) 113.9(1) S(1)-Si(2)-C(7) 96.80(9) S(2*)-Si(2)-C(7) 111.5(3)

2.132(2) 2.139(2) 2.125(2) 1.895(7)

Table 3. Selected Bond Lengths (Å), Nonbonding Distances (Å), and Bond Angles (deg) for 2 Bond Lengths 2.282(2) Si(2)-Se(3) 1.911(7) Si(2)-Se(1*) 2.282(2) Si(1)-Se(2) 2.276(2) Si(1)-C(1)

Si(2)-Se(2) Si(2)-C(7) Si(1)-Se(1) Si(1)-Se(3)

Nonbonding Atom Distances 2.99 Se(2)-Se(3) 5.66

3.19

Si(1)-Si(2) Se(1)-Se(1*)

82.91(9) 114.54(9) 103.0(2) 117.6(3) 114.37(10) 104.1(2) 116.5(3)

Se(2)-Si(2)-Se(3) Se(2)-Si(2)-Se(1*) Se(3)-Si(2)-Se(1*) Se(1)-Si(1)-Se(2) Se(1)-Si(1)-C(1) Se(2)-Si(1)-C(1) Si(1)-Se(1)-Si(2*) Si(2)-Se(3)-Si(1)

The NMR spectra of 1-4 are consistent with the X-ray crystal structures. Reflecting their high symmetry, 1 and 2 showed only one resonance in the 29Si{1H} NMR spectrum, indicating that all silicon atoms are equivalent. The 77Se NMR spectra of 2 and 4 are worthy of note. The corresponding spectrum reveals two resonances at -51.7 and -122.2 ppm for 2 and at 154.0 and -3.2 ppm for 4. The data indicate that the selenium atoms in the four-membered rings and those bridging the two four-membered rings are not equivalent.14 In 1H and 13C NMR spectra, one kind of thexyl groups is observed for all 1-4. (14) In ref 2f, Bahr and Boudjouk pointed out that 77Se NMR would descriminate adamantane-like and double-decker-like structures.

2217

Bond Angles 97.59(5) Se(2)-Si(2)-C(7) 115.17(8) Se(3)-Si(2)-C(7) 113.48(7) C(7)-Si(2)-Se(1*) 114.50(8) Se(1)-Si(1)-Se(3) 103.0(2) Se(2)-Si(1)-Se(3) 117.9(3) Se(3)-Si(1)-C(1) 108.39(6) Si(2)-Se(2)-Si(1) 82.30(6)

2.273(2) 2.279(2) 2.275(2) 1.912(7) 3.43

116.7(2) 110.1(2) 104.0(2) 114.45(7) 97.69(6) 109.8(2) 82.14(6)

Compounds 1, 3, and 4 are thermally unstable. When 1 or 3 was heated in decahydronaphthalene at 190 °C for 24 h, the starting materials disappeared and single products were generated. From the results of mass and NMR spectra, both compounds could be assigned as the adamantane-type hexasulfides 5 and 6. The 29Si chemical shift of 5 was 26.0 ppm, and this value is in good agreement with those of adamantane-type tetrasilathianes (17.0 ppm for Me4Si4S6,2f 21.5 ppm for Et4Si4S6,2f and 29.3 ppm for t-Bu4Si4S610). The yields were 57% for 5 and quantitative for 6. Such an isomerization of double-decker to adamantane-type structure was first observed for (t-Bu2Ge2S2)2S2 over 200 °C.7 Interestingly, germanium-selenium derivative 4 showed skeletal rearrangement to 7 at a much lower temperature, 80

Tricyclotetrasilachalcogenanes and -tetragermachalcogenanes

Organometallics, Vol. 16, No. 20, 1997 4431

Figure 1. ORTEP drawing of 1-4. Thermal ellipsoids are drawn at the 30% probability level. Table 4. Selected Bond Lengths (Å), Nonbonding Distances (Å), and Bond Angles (deg) for 3 Bond Lengths 2.224(2) Ge(1)-S(2) 2.232(1) Ge(1)-C(1) 2.229(1) Ge(2)-S(3) 1.990(6) Ge(2)-S(1*)

Ge(1)-S(1) Ge(1)-S(3) Ge(2)-S(2) Ge(2)-C(7) Ge(1)-Ge(2) S(1)-S(1*)

Nonbonding Atom Distances 2.98 S(2)-S(3) 5.57

S(1)-Ge(1)-S(2) S(1)-Ge(1)-C(1) S(2)-Ge(1)-C(1) S(2)-Ge(2)-S(3) S(2)-Ge(2)-S(1*) S(3)-Ge(2)-S(1*) Ge(1)-S(1)-Ge(2*) Ge(1)-S(3)-Ge(2)

Bond Angles 113.41(6) S(1)-Ge(1)-S(3) 105.0(6) S(2)-Ge(1)-S(3) 110.1(2) S(3)-Ge(1)-C(1) 95.76(5) S(2)-Ge(2)-C(7) 114.25(6) S(3)-Ge(2)-C(7) 114.57(6) C(7)-Ge(2)-S(1*) 109.22(6) Ge(1)-S(2)-Ge(2) 84.21(5)

2.227(2) 1.996(6) 2.226(2) 2.227(2)

Table 5. Selected Bond Lengths (Å), Nonbonding Distances (Å), and Bond Angles (deg) for 4 Bond Lengths 2.358(2) Se(1)-Ge(2*) 2.363(1) Se(1)-Ge(2) 2.361(2) Se(3)-Ge(2) 1.98(1) Ge(2)-C(7)

Se(1)-Ge(1) Se(2)-Ge(1) Se(3)-Ge(1) Ge(1)-C(1)

Nonbonding Atom Distances 3.13 Se(2)-Se(3) 5.94

3.30

Ge(1)-Ge(2) Se(1)-Se(1*)

114.69(6) 95.64(5) 118.1(2) 109.8(2) 119.1(2) 103.7(2) 84.22(5)

Ge(1)-Se(1)-Ge(2*) Ge(1)-Se(3)-Ge(2) Se(1)-Ge(1)-Se(3) Se(2)-Ge(1)-Se(3) Se(3)-Ge(2)-C(1) Se(2)-Ge(2)-C(7) Se(3)-Ge(2)-C(7) C(7)-Ge(2)-Se(1*)

°C in C6H6. These results show that the germaniumselenium framework is more labile, probably due to a lower Ge-Se bond energy. The identification of 7 was effected by 77Se NMR (single peak at -6.1 ppm) and other spectral data. The structures of 6 and 7 also were confirmed by X-ray crystallography.15 The skeletal rearrangement also was observed when the crystal was heated in a nitrogen atmosphere. Thus 1, 3, and 4 were converted to adamantane-type 5-7 at their melting points (Scheme 2). It is also indicated again that the double-decker compound is the kinetically controlled

Bond Angles 107.07(5) Ge(1)-Se(2)-Ge(2) 83.09(5) Se(1)-Ge(1)-Se(2) 113.48(2) Se(1)-Ge(1)-C(1) 96.77(5) Se(2)-Ge(1)-C(1) 109.6(3) Se(2)-Ge(2)-Se(3) 118.7(3) Se(2)-Ge(2)-Se(1*) 110.0(3) Se(3)-Ge(2)-Se(1*) 102.7(3)

2.364(2) 2.358(2) 2.362(1) 1.98(1) 3.53

83.14(5) 115.40(6) 104.7(3) 117.0(3) 96.86(5) 114.61(6) 114.53(6)

product and the adamantane-type compound is the thermodynamically controlled product, as in the case of t-Bu4Ge4S6. The proposed reaction pathway for the skeletal rearrangement is shown in Scheme 3. On the (15) Due to the severe disorder of substituents, presumably caused by sphere shape of the molecule, we could not determine the position of carbon atoms; however, the adamantane-like framework was unequivocally established. Crystal data, 6: C24H52Ge4S6, orthorombic, Pna21, a ) 12.313(3) Å, b ) 17.154(3) Å, c ) 17.490(3) Å, V ) 3694(2) Å3, Z ) 4, R ) 0.073, Rw ) 0.080. 7: C24H52Ge4Se6, orthorombic, P212121, a ) 20.572(3) Å, b ) 20.782(3) Å, c ) 17.026(3) Å, V ) 7279(1) Å3, Z ) 8, R ) 0.092, Rw ) 0.083.

4432 Organometallics, Vol. 16, No. 20, 1997

Unno et al.

Scheme 2

Figure 2. UV spectra of 1-4 in cyclohexane.

Scheme 3

other hand, silicon-selenium analogue 2 was stable to its melting point (272 °C) and no rearrangement was observed.16 UV Spectra. The electronic spectra of silicon and germanium sesquichalcogenides have not been appeared so far to our best knowledge. We found that the doubledeckers 1-4 show an absorption above 200 nm in the UV region. Data for these compounds are shown in Figure 2. Although 1 shows only end absorption, 2 and 3 exhibited absorption maxima as shoulders at 232 ( 16 000) and 236 nm ( 23 000), respectively. Interestingly, 4 shows two absorption maxima (274 nm,  16 000; 229 nm,  38 000), and the band edge is tailing into the visible region. UV-visible spectra of adamantane-type 5-7 in cyclohexane are shown in Figure 3. Similarly, only 7 shows an absorption maximum (221 nm,  37 000) and shoulder (238 nm,  26 000). Although the reasons why these transitions are allowed and why the double-decker compounds show higher absorption maximum are not yet understood, the optical properties of these cage systems are of considerable interest. We are now investigating their electronic properties including emission spectra for interpreting these unique systems. In summary, treatment of thexyltrichlorogermane or thexyltrichlorosilane with lithium sulfide or selenide (16) The reason why only 2 did not rearrange to an adamantanetype compound is not clear. We postulate that there are two factors for the rearrangement. One is the bond strength; thus, the Ge-Se compound rearranged most readily. The second is steric hindrance of the starting double-decker compounds. Compared to the Si-S bond, Si-Se bond is longer and that releases the strain and decreases reactivity.

Figure 3. UV spectra of 5-7 in cyclohexane.

gave double-decker hexachalcogenide 1-4, and those were stable to hydrolysis. The structures were determined by X-ray crystallography. Double-deckers were converted to the adamantane type by heating, except for the silicon-selenium system. Further reactions of these unique skeleton compounds are now investigated. Experimental Section All solvents used in the reactions were purified and dried by the reported methods. Lithium aluminum hydride was used in the case of hydrocarbons such as benzene and hexane. THF was purified by distillation from benzophenone ketyl prior to use. Hydrocarbons for recrystallization were used after distillation. All reactions were carried out under an argon or dry nitrogen unless otherwise noted. Lithium sulfide, selenium, LiEt3BH, 2,3-dimethyl-2-butene, R,R′-azobis(isobutyronitrile) (AIBN), trichlorosilane, and trichlorogermane were commercially available and used without further purification. Nuclear magnetic resonance spectra were obtained by a JEOL R-500 spectrometer. Dimethyl selenide was used as

Tricyclotetrasilachalcogenanes and -tetragermachalcogenanes external standard in 77Se NMR. Mass spectrometry was measured by a Jeol JMS-DX302 instrument. Infrared spectra were recorded with Jasco A-102 spectrometer. GLC analysis was carried out by Shimadzu GC-8A instrument using a glass packed column (f i.d. 3.5 × 1000 mm) with 10% silicon KF-96 on Celite 545 sk. Preparative HPLC was performed on an LC09 instrument with JAI gel 1H+2H columns, and chloroform was used as eluent. Preparation of (1,1,2-Trimethylpropyl)trichlorosilane. This trichlorosilane was prepared by a reported method.17 Trichlorosilane (40.3 g, 0.30 mol), 2,3-dimethyl-2-butene (8.9 g, 0.11 mol) and AIBN (3.0 g, 18.3 mmol) were charged in a stainless steel autoclave, and the mixture was heated to 120 °C for 24 h. After cooling the reaction mixture, the remaining AIBN was removed by filtration, and filtrate was distilled under reduced pressure to afford ThexSiCl3 (31.8 g, 69%) as colorless liquid: bp 46-49 °C (6 mmHg); 1H NMR (CDCl3) δ 1.01 (d, 6H, J ) 6.8 Hz), 1.12 (s, 6H), 1.95 (sept, 1H, J ) 6.8 Hz); 13C NMR (CDCl3) δ 18.53, 19.32, 23.45, 33.25; 29Si NMR (CDCl3) δ 16.90. Preparation of (1,1,2-Trimethylpropyl)trichlorogermane. This trichlorogermane was prepared by reported methods.18 Trichlorogermane (37.8 g, 0.21 mol) was slowly added to 2,3-dimethyl-2-butene (17.7 g, 0.21 mol) at 0 °C. After the addition, the reaction mixture was warmed to room temperature and stirred for 12 h. The reaction mixture was distilled under reduced pressure to afford ThexGeCl3 (42.3 g, 77%) as colorless liquid: bp 58-62 °C (4 mmHg); 1H NMR (CDCl3) δ 1.06 (d, 6H, J ) 7.0 Hz), 1.32 (s, 6H), 2.14 (sept, 1H, J ) 7.0 Hz); 13C NMR (CDCl3) δ 18.63, 20.03, 34.59, 53.63. Synthesis of Tetrakis(1,1,2-trimethylpropyl)-2,4,6,8,9,10-hexathia-1,3,5,7-tetrasilatricyclo[5.1.1.13,5]decane (1). To a suspension of Li2S (1.0 g, 22.1 mmol) in THF (35 mL) was added a solution of ThexSiCl3 (2.9 g, 13.4 mmol) in THF (20 mL) over 1 h at 0 °C. The reaction mixture was warmed to room temperature and stirred for 2 weeks. After removal of THF, benzene was added to the residue to precipitate insoluble salts and the solution was filtered. The filtrate was concentrated in vacuo. Hexane was added to the residue, resulting in precipitaion of white crystals which were filtered and recrystallized from hexane to give 1 (0.55 g, 25%) as colorless crystals: mp 267-269 °C; 1H NMR (CDCl3) δ 0.95 (d, 24H, J ) 6.7 Hz), 1.10 (s, 24H), 2.06 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl3) δ 18.49, 18.91, 33.81, 34.01; 29Si NMR (CDCl3) δ 17.43; MS (70 eV) m/z (%) 644 (M+, 31), 349 (base). Anal. Calcd for C24H52Si4S6: C, 44.66; H, 8.12. Found: C, 44.70; H, 8.30. Synthesis of Tetrakis(1,1,2-trimethylpropyl)-2,4,6,8,9,10-hexaselena-1,3,5,7- tetrasilatricyclo[5.1.1.13,5]decane (2). A solution of LiEt3BH (12.5 mmol in 12.5 mL of THF) was added dropwise to elemental selenium (0.45 g, 5.7 mmol) via syringe. After the addition, THF (6 mL) was added and the mixture was stirred for 1 h at room temperature. A solution of ThexGeCl3 (0.80 g, 3.6 mmol) in THF (10 mL) was added to the Li2Se solution over 1 h at 0 °C. After the addition, the reaction mixture was warmed to room temperature and stirred until the red color of the selenium salt had disappeared (∼5 days). THF was removed in vacuo, and benzene was added to precipitate insoluble salts. The filtrate was concentrated, and residue was recrystallized from benzene to afford 2 (0.36 g, 43%): colorless crystals, mp 272-274 °C; 1H NMR (CDCl3) δ 0.98 (d, 24H, J ) 6.7 Hz), 1.13 (s, 24H), 2.08 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl3) δ 18.80, 19.30, 33.75, 34.75; 29Si NMR (CDCl ) δ -3.80; 77Se NMR (CDCl ) δ -122.2, -51.7; 3 3 MS (70 eV) m/z (%) 928 (M+, 7), 85 (base). Anal. Calcd for C24H52Si4Se6: C, 31.10; H, 5.66. Found: C, 31.49; H, 5.69. Synthesis of Tetrakis(1,1,2-trimethylpropyl)-2,4,6,8,9,10-hexathia-1,3,5,7-tetragermatricyclo[5.1.1.13,5]decane (17) Kawano, Y.; Tobita, H.; Ogino, H. J. Organomet. Chem. 1992, 428, 125. (18) Fischer, A. K.; West, R. C.; Rochow, E. G. J. Am. Chem. Soc. 1954, 76, 5878.

Organometallics, Vol. 16, No. 20, 1997 4433 (3). To a suspension of Li2S (1.0 g, 22.1 mmol) in THF (30 mL) was added a solution of ThexSiCl3 (3.8 g, 14.2 mmol) in THF (15 mL) over 1 h at 0 °C. The reaction mixture was warmed to room temperature and stirred for 24 h. After removal of THF, benzene was added to the residue to precipitate insoluble salts and the mixture was filtered. The filtrate was concentrated in vacuo. Hexane was added to the residue. The resulting white crystals were filtered and recrystallized from benzene/hexane to give 3 (1.6 g, 55%) as colorless crystals: mp 217-219 °C; 1H NMR (CDCl3) δ 0.97 (d, 24H, J ) 6.7 Hz), 1.26 (s, 24H), 2.15 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl3) δ 18.80, 19.80, 34.92, 48.15; MS (30 eV) m/z (%) 824 (M+, 1), 85 (base). Anal. Calcd for C24H52Ge4S6: C, 35.01; H, 6.36. Found: C, 35.24; H, 6.45. Synthesis of Tetrakis(1,1,2-trimethylpropyl)-2,4,6,8,9,10-hexaselena-1,3,5,7- tetragermatricyclo[5.1.1.13,5]decane (4). Preparation of Li2Se was effected in the same manner as described above. A solution of ThexGeCl3 (0.99 g, 3.8 mmol) in THF (10 mL) was added to this solution over 1 h at 0 °C. After the addition, the reaction mixture was warmed to room temperature and stirred until the red color of the selenium salt had disappeared (∼24 h). THF was removed, and hexane was added to precipitate insoluble materials. After the filtration, the precipitate was extracted with benzene and the insoluble salts were removed by filtration. The benzene solution was concentrated and the residue was recrystallized from benzene/pentane below 60 °C to afford 4 (0.54 g, 52%): pale yellow crystals, mp >275 °C; 1H NMR (CDCl3) δ 0.98 (d, 24H, J ) 6.7 Hz), 1.21 (s, 24H), 2.13 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl ) δ 19.01, 19.91, 35.86, 46.66; 77Se NMR 3 (CDCl3) δ -3.1, 154.0; MS (70 eV) m/z (%) 1106 (M+, 1), 85 (base). Anal. Calcd for C24H52Ge4Se6: C, 26.09; H, 4.74. Found: C, 26.35; H, 4.72. Thermal Reaction of 1. A solution of 1 (137 mg, 0.21 mmol) in decahydronaphthalene (80 mL) was refluxed for 24 h. After removal of decahydronaphthalene in vacuo, the residue was separated by (GPC) and recrystallized from EtOH to afford 5 (78 mg, 57%): colorless crystals, mp 211-213 °C; 1H NMR (CDCl ) δ 1.01 (d, 24H, J ) 6.7 Hz), 1.10 (s, 24H), 3 2.01 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl3) δ 19.00, 19.22, 32.48, 33.47; 29Si NMR (CDCl3) δ 26.00; MS (70 eV) m/z (%) 644 (M+, 13), 84 (base). Anal. Calcd for C24H52Si4S6: C, 44.67; H, 8.12. Found: C, 44.69; H, 8.23. Thermal Reaction of 3. A solution of 3 (203 mg, 0.25 mmol) in decahydronaphthalene (80 mL) was refluxed for 24 h. After removal of the decahydronaphthalene in vacuo, the residue was separated by (GPC) and recrystallized from EtOH to afford 6 (quantitative) as colorless crystals: mp 232-235 °C; 1H NMR (CDCl3) δ 1.02 (d, 24H, J ) 7.0 Hz), 1.22 (s, 24H), 2.08 (sept, 4H, J ) 7.0 Hz); 13C NMR (CDCl3) δ 18.97, 20.43, 34.56, 46.45; MS (30 eV) m/z (%) 824 (M+, 0.3), 85 (base). Anal. Calcd for C24H52Ge4S6: C, 35.01; H, 6.36. Found: C, 35.18; H, 6.44. Thermal Reaction of 4. A solution of 4 (73.1 mg, 66.2 mmol) in benzene (20 mL) was refluxed for 24 h. After removal of benzene in vacuo, the residue was separated by GPC and recrystallized from hexane to afford 7 (quantitative) as colorless crystals: mp >270 °C; 1H NMR (CDCl3) δ 1.06 (d, 24H, J ) 6.7 Hz), 1.23 (s, 24H), 2.11 (sept, 4H, J ) 6.7 Hz); 13C NMR (CDCl3) δ 19.18, 21.48, 35.48, 45.49; 77Se NMR (CDCl3) δ -3.46; MS (30 eV) m/z (%) 1095-1117 (M+), 85 (base). Anal. Calcd for C24H52Ge4Se6: C, 26.09; H, 4.74. Found: C, 26.14; H, 4.80. X-ray Crystallography (General Procedure). Intensity data were collected on a Rigaku AFC7S diffractometer at 20 ( 1 °C with Cu KR radiation (λ ) l.541 78 Å) and the ω-2θ scan technique to a maximum value of 120.1°. An empirical absorption correction was applied. The data were corrected for Lorenz and polarization effects. The structure was solved

4434 Organometallics, Vol. 16, No. 20, 1997 by SHELXS86.19 The positions of all hydrogen atoms were calculated. For 1, 18 hydrogen atoms were refined isotropically, and the rest were included in fixed position. For 2-4, hydrogen atoms were included but not refined. All calculations were performed using the teXsan20 software of the Molecular Structure Corp.

Acknowledgment. This work was supported by a Grant-in-aid from the Ministry of Education, Science, (19) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University Press: Oxford, U.K., 1985; p 175. (20) teXsan: Crystal Structure Analysis Package, Molecular Structure Corp., The Woodlands, TX, 1985, 1992.

Unno et al.

and Culture of Japan. We also thank Shin-Etsu Chemical Co. Ltd. and Chisso Co. Ltd for the gift of silicon reagents and Asai Germanium Research Institute Co. Ltd for germanium reagents. Supporting Information Available: X-ray analysis experiment for 1-4 including tables of anisotropic thermal parameters, atomic coordinates and isotropic thermal parameters, bond lengths and angles, and figures showing the molecular and views of molecular packing (78 pages). Ordering information is given on any current masthead page. OM970432R